An enzyme from Fusarium incarnatum exhibiting diglycosidase and α-L-rhamnosidase activities catalyses the biotransformation of naringin to naringenin.

This study reports the purification, characterization and biotransformation potential of a unique enzyme from a newly isolated fungal strain, Fusarium incarnatum exhibits dual diglycosidase and α-L-rhamnosidase activities. The enzyme was purified to homogeneity using ion-exchange and gel filtration chromatography. It exhibited maximal enzyme activity at 70 °C and pH 10. Steady-state kinetic analysis using both natural and synthetic substrates revealed high substrate affinity and catalytic efficiency, as evidenced by the calculated kcat/Km values of 11.0 mM-1 s-1 and 18.7 mM-1 s-1 for naringin and p-nitrophenyl-α-L-rhamnopyranoside (pNPR), respectively. The purified enzyme catalyzed one-step hydrolysis of naringin to naringenin, accompanied by the release of neohesperidose. The formation of both products was confirmed by LC-MS analysis, and the formation of neohesperidose was further validated by (1D) 1H NMR analysis. This single step conversion indicates diglycosidase activity, distinguishing it from classical monoglycosidase activity of α-L-rhamnosidase. Such catalytic efficiency toward the α-L-rhamnosyl-(1 → 2)-β-d-glucose moiety in neohesperidose containing flavonoids highlights its potential for one-step biotransformation of naringin to naringenin.